Exactly when the Byzantine Empire began is a matter of some debate. The Byzantines themselves considered themselves (with some reason) indivisible from the Roman Empire, and so would say that their empire began when the legendary Romulus (allegedly descended from the Trojans of antiquity) founded a city and populated it with the unwanted dregs of the city states of Italy. From this unlikely beginning came the great Roman Empire, and that is what the Byzantines believed themselves to be.

Of course, there are those who dispute that claim. To many historians, without Rome the Empire is not Roman. And the European contemporaries of Byzantium wished to claim the hallowed mantle of the Roman Empire for themselves, so they derisively referred to them as the Greek Empire, that being the language they had traded Latin for. Victorian historians dubbed them the Byzantine Empire, after the Greek city of Byzantium that was remade as their capital. It is definite that they were something different from what we think of as Romans, anyway. But where did that difference come from?

The Roman General Pompeius Gnaeus Magnus, commonly known as Pompey, was a key figure in the fall of the Republic and the birth of the Roman Empire. His key contribution to the foundation of the Byzantine Empire, however, came several years prior to those incidents. Pirate raids in the Mediterranean had become a serious problem for the Empire, disrupting trade and vital supplies that kept Rome’s citizens fed. The pirates found safe harbour in the kingdom of Anatolia, whose king, Mithridates, had long been a thorn in Rome’s side. While the first general Rome sent against him, Lucullus, had a reasonable amount of success, Pompey felt that he could do better. He persuaded the Senate to grant him the command of the armies in the war, and went on to both sweep the pirates from the sea and destroy the land bases they retreated to. In 66BC, Pompey was able to move against Mithridates. He forced him back, conquering and annexing the province of Pontus (where Constantinople would one day stand) and Syria, among others. Pompey went on to stabilise the rest of the Roman-controlled territories (including Judea), and before he returned to Rome had established the territories that would be the heart of first the Eastern Roman Empire, and then the Byzantine Empire.

The next step in the establishment of the Byzantine Empire came in 285AD, when the Emperor Diocletian divided the Empire between himself and his co-emperor, Maximian. There had been co-emperors before, and even rulers in the east and the west, but Diocletian’s division was far more official, and was intended to be a permanent division. Each man was declared Augustus, and each had a junior Caesar as heir apparent. In The Decline and Fall of the Roman Empire, Gibbon lists each man’s sphere of influence:

“The defence of Gaul, Spain, and Britain was entrusted to Constantius: Galerius was stationed on the banks of the Danube, as the safeguard of the Illyrian provinces. Italy and Africa were considered as the department of Maximian; and for his peculiar portion Diocletian reserved Thrace, Egypt, and the rich countries of Asia.”

We can see here that Diocletian, the senior Augustus, reserved for himself the provinces that would later become the heart of the Eastern Empire. This reflected both the general shift away from Rome of imperial authority, and marked a deliberate division between his sphere of influence and that of Maximian. While the Tetrarchy that he had established was too fragile a structure to survive his abdication and retirement, before the Empire was reunified the concept of an Empire of two halves had been firmly established by nearly forty years of official separation.

Ironically it was the man who re-unified the Empire in 324AD who would go on to lay the cornerstone of the eventual Byzantine Empire. The son of Constantius Chlorus, part of Diocletian’s Tetrarchy, Constantine the Great was raised in Diocletian’s eastern court at Nicomedia. Nicomedia was at the time the capital of the Eastern Empire, in the province of Bithynia. Constantine’s mother Helena was from Bithynia, so it would not be surprising that he found the province to his liking. He fought in several wars against the Persians among other foes, under both Diocletian and under his father’s fellow Caesar, Galerius. Gibbon paints a picture of the young Constantine as a serious young man, clearly showing signs of the glory he would achieve:

“The figure of Constantine was tall and majestic; he was dexterous in all his exercises, intrepid in war, affable in peace; in his whole conduct the active spirit of youth was tempered by habitual prudence; and while his mind was engrossed by ambition, he appeared cold and insensible to the allurements of pleasure.”

Despite his father’s station, however, Constantine was attainted by the fact that Constantius had been forced to divorce his mother and marry the stepdaughter of Maximian to become Caesar. As such, he became an easy target of the jealousy that Galerius felt towards his father. After Diocletian’s abdication, there was a general expectation that Constantine would be appointed as one of the new Caesars. Instead, however, Maximinus (a nephew of Galerius) and Severus (an old friend of Galerius) were both elevated to the purple. Constantine was forced to flee the court of Nicomedia and join his father, who was at that point in the process of invading Britain.

On Constantius’ death, his troops hailed Constantine as Augustus, a de facto arrangement that the other Tetrarchs found themselves obliged to honour. Similarly, the son of Maximian, Maxentius, was hailed as Emperor in Rome, and seized control of Italy. There were now six Emperors, and civil war was inevitable. Several wars were fought between the Emperors before the empire was reunited under Constantine, however only two pertain directly to the foundation of Byzantium. The first is the war between Maxentius and Constantine, which culminated at the Battle of the Milvian Bridge, where Constantine defeated Maxentius. This is notorious as the battle where Constantine fought beneath the symbol of Christianity, often taken as the moment when Christianity became an accepted part of the Empire and the imperial system. It is this unification of head of state and defender of the faith that comes to personify the Byzantine emperors. The second is the war between Licinius and Constantine, the last war of the reunification. Licinius was another emperor who had been raised to the purple by Galerius, and he now stood as the sole ruler of the eastern empire, while Constantine controlled the west. The two fought several wars, and it was in the final one of these that the forces of Constantine laid siege to the city of Byzantium. The highly defensible location of the city no doubt remarked itself to Constantine at the time. The war ended with the defeat of Licinius at Chrysopolis. The Roman Empire once again was ruled by a single emperor.

While this reunification of Rome might seem a step backwards from the evolution of the Eastern Empire as a separate entity, it was what Constantine did next that created the Byzantine Empire as we know it. Rome had become a less than perfect capital for the empire, with a fractious senatorial class who had already chosen and raised up one Emperor of their own. Constantine dealt with this by heavily taxing the senators, disbanding the Praetorian Guard who had long served as kingmakers, and finally, by simply ignoring Rome entirely. It is reported that he returned to Rome only twice more in the course of his life. On the tenth and twentieth anniversaries of his reign he returned to observe the pagan ceremonies to the Roman gods that marked those dates, although he did not return for the thirtieth anniversary. Beyond those visits, however, Rome was now officially a backwater of the empire that bore her name.

The other main centre of the Roman world at the time was Nicomedia, the capital of Bithynia where Diocletian had established his court. While Constantine made Nicomedia his temporary capital from 324BC to 330BC, he never had any intention of making it the permanent set of power. Whether it was (as Gibbon suggests) that Nicomedia was associated in the Christian mind with the persecutions of Diocletian and Galienus, or whether it was an issue of defensibility, or whether it was some other reason is impossible to truly say. All we know is that despite his having to flee the city decades earlier, it is unlikely to have been any personal animosity towards it that prompted him. The imperial villa remained in Nicomedia and was in fact where Constantine would be baptised and die in 337AD. Perhaps it was simply a desire to leave an indelible mark on the empire and establish a New Rome that would forever be associated with his name. Constantine himself is said to have claimed divine inspiration for his choice.

Regardless, Constantine determined to found a new capital for his empire. The site he settled upon, Byzantium, had featured in the war against Licinius. Crispin, the son of Constantine, had laid siege to it, and Constantine had seen firsthand how the Greek city was admirably suited for defence, not to mention the advantages for trade in having such a large harbour and such a commanding position on the trade routes between Asia and Europe. He made the choice in 324BC, and spent six years building the city before moving there in 330BC. To construct the city, Constantine endowed entire schools of architectures, as well as ransacking the artistic treasure of the rest of the empire to adorn the new capital. The end result was a city well suited for a capital, with a great Imperial palace, a public forum on the site of Constantine’s camp during the siege of Byzantium, a great hippodrome, public baths and other amenities that the Romans regarded as the necessities of civilisation.

But no more important than the city were the people who would go on to become the Byzantines. Constantine invited those nobles from Rome and other parts of the Empire who he favoured to come to his new capital and construct their homes, offering them gifts of land to offset the expense of the move. He also established a rule that no man could enter Imperial service in Asia Minor unless he built a home in his new capital. But it was the native Greek population who would go on to shape the character of the Byzantine Empire most profoundly, leading the medieval Europeans to refer to it as “the Greek Empire” rather than “the Roman Empire”.

Constantinople (as it became known, although at this time it was simply “New Rome”) would be the heart of the Byzantine Empire. In the eyes of some, this was the recreation of Rome, leading some to call him “the first Byzantine Emperor”. However the Roman Empire remained unified until 395BC, when Theodosius I died and left the empire to be divided between his two sons. Arcadius inherited the Eastern Empire, and Honorius the Western. From this point on the two empires were permanently divided, and it is the Eastern Empire ruled by Arcadius that continued on past the fall of the West to become known as the Byzantine Empire.

After this division, other factors emerged to shape the character of the Byzantines. Their weaponry and clothing adapted to the heat of their new homes, and the fashions of their neighbours. Their religion developed its own path, separate from that of Latin Christianity, leaded to both the worship of and reaction against sacred ikons that seemed baffling to many in the West. The lack of a belief in the “Divine Right Of Kings” that stabilised monarchies in the West led to the backstabiing Byzantine politics that is their most enduring impression. And the Emperor Heraclius (a pivotal figure in Byzantine history for many reasons)  in the 7^th century chose to discard Latin as the language of administration, and formalise what had been the de facto reality for many years by making Greek the official language of the Empire. The language of the Romans was no more. The “Greek Empire” was born.